Thermal insulation technique for ultra low temperature cryogenic processor

ABSTRACT

Systems and methods are disclosed to provide a cryogenic processor apparatus with an outer housing; an inner housing coupled to the external housing to define a vacuum region there between; and material disposed in the vacuum region to provide redundant insulation and structural support at a cryogenic temperature.

This application is a continuation of application Ser. No. 11/934,696filed on Nov. 2, 2007 and 12/984,206, filed Sep. 30, 2010, the contentof which is incorporated by reference.

BACKGROUND OF THE INVENTION

This invention relates to a thermal insulation technique for ultra lowtemperature cryogenic processors.

Vacuum insulating panels are used conventionally for thermal insulation.Known vacuum insulating panels consist of a pre-compressed porousfilling, a porous pressboard or an open-cell rigid foam as substrate,which is enveloped by a gas-tight film, wherein the film is heat-seatedor bonded after the evacuation.

The following, for example, are used as filling materials for vacuuminsulating panels: precipitated and dried silicas, silica gels, fly ash,open-cell foams on an organic base such as open-cell rigid polyurethanefoams or bonded rigid polyurethane foam paste. Vacuum insulating panelsof this type are used in the manufacture of cold rooms, e.g.,refrigerators or refrigerated containers, with the latter being insertedbetween the outer and inner casing and the gap left between the outerand inner casing being filled with foam.

The fitting of the vacuum insulation panels into refrigerator casingsnevertheless presents problems. According to the current state of theart, they are bonded onto a plate—for example, a metal cassette—by meansof a double-sided adhesive film. This combination plate can then beprocessed further into a sandwich panel, for example, a refrigeratordoor, wherein the cavity left is conventionally filled with foam.

As a result, on the one hand, a complicated, multi-step process isrequired, and on the other hand, the insulation volume is affected bythe foam, which is less efficient in insulation terms when compared witha vacuum insulation panel. Arrangements of this type are also, to only alimited extent, without thermal bridges.

U.S. Pat. No. 6,164,030 discloses an apparatus which consists of a rigidplate and a vacuum insulation panel, in which the vacuum insulationpanel is fixed to the rigid plate by a polyurethane foam applied as aliquid reaction mixture, wherein the vacuum insulation panel containsopen-cell rigid plastics foam and/or open-cell rigid plastics foamrecyclate.

SUMMARY

In a first aspect, systems and methods are disclosed to provide acryogenic processor apparatus with an outer housing; an inner housingcoupled to the external housing to define a vacuum region there between;and material disposed in the vacuum region to provide redundantinsulation and structural support at a cryogenic temperature.

In another aspect, systems and methods are disclosed to provide an ultralow temperature (ULT) cryogenic processor apparatus. The apparatusincludes an external housing with flat sides; an inner housing coupledto the external housing to define a vacuum region there between;material disposed in the vacuum region to provide redundant insulationand structural support; and a cryogenic heat exchanger contained in theinner housing.

Implementations of the above aspect may include one or more of thefollowing. The material can be an insulation material with one of: asilica micro balloon, polyisocyanurate. The vacuum region can beprocessed by removing residual water vapor and other partial pressure ofcontaminants. The vacuum region is evacuated to a partial pressure ofapproximately 0.2 milliTorr. The cryogenic heat exchanger can includeone or more tubings and may include redundant tubings. The cryogenicheat exchanger can be U-shaped tubings covering at least three walls ofthe payload bay. The cryogenic heat exchanger can include tubingscovering at least four sides of the payload bay. Alternatively, thecryogenic heat exchanger can be one or more coils positioned on the topand/or the bottom of the vessel. A port can connect to the one or moretubings to provide input and output connections thereto. A door canallow access to the payload bay, wherein the door comprises three ormore materials having different thermal characteristics.

In another aspect, a method to provide ultra low temperature processingand/or storage includes providing insulation and structural supportusing a material disposed in a vacuum region between an external housingand an inner housing; and cryogenically processing one or morecompartments contained in the payload bay.

Implementations of the above aspect may include one or more of thefollowing. The material can be an insulation material with silica microballoon technology. The process can remove water vapor, partial pressurecontaminates and atmospheric gases from the vacuum region. The processincludes evacuating the vacuum region to approximately 0.2 millitorr.The cryogenic heat exchanger can have one or more heat exchange tubings,and can include redundant tubings. The redundant tubings can be acomplete set of heat exchange tubings operating in parallel with theprimary heat exchange tubings. The redundant tubings can have one ormore tubings branched from the primary heat exchange tubings. Thecryogenic heat exchanger can also include U-shaped tubings covering atleast three walls of the inner housing. The tubings can cover at leastfour sides of the inner housing. A door can be formed with a pluralityof materials each having different thermal characteristics. A changeablerack assembly is supported in the chamber. The system can transmitenergy from the payload bay into the heat exchanger through thechangeable rack assembly. A negative pressure in the payload bay can bemaintained through the use of pneumatic seals on the main door assembly.The cryogenics vacuum pumping via the heat exchanger can provide energyremoval from the payload bay and into the heat exchanger. The surfacesof at least one of the external and inner housing can be flat surfaces.

In another aspect, a method to insulate a vessel includes placing aplurality of shells on all sides of the vessel without providing adirect energy pathway from outer walls of the vessel to the inner wallsof the vessel; placing the shells under a vacuum; cryogenically coolingthe shells to a cryogenic temperature; and while under vacuum, allowingthe shell temperature to rise from the cryogenic temperature to ambienttemperature.

Implementations of the above aspect may include one or more of thefollowing. The process can include milling spaced-apart pathways in theshells. Such millings facilitate an evacuation of the trapped spaces ofthe shells and allowing for a desorbtion of a surface area of theshells. A vacuum pump can maintain a partial pressure of the vacuum inthe vessel to below approximately 10 millitorr. The vacuum pump is anon-oil based pump. Initially, the process evacuates the shells to atotal pressure of approximately 500 millitorr. The process thencryogenically cools the shells to a temperature of less thanapproximately −175° C. Next, gettered gases can be removed by a pseudothermo/kinetic energy transfer during the rise to ambient temperature.The shells can be a foam material. The shell layout prevents heat gainenergy from migrating from the outer walls to the inner walls bypresenting at least two 90 degree flow pathway changes.

In another aspect, an insulated vessel includes outer walls; inner wallsspaced apart from the outer walls to define a vacuumed insulationvolume; and a plurality of shells placed in the insulation volumewithout providing a direct energy pathway from outer walls of the vesselto the inner walls of the vessel, wherein the shells are cryogenicallycooled to a cryogenic temperature and while under vacuum, the shelltemperature is raised from the cryogenic temperature to ambienttemperature.

Implementations of the above aspect may include one or more of thefollowing. Spaced-apart pathways can be milled in the shells. Thepathways facilitate an evacuation of the trapped spaces of the shellsand allowing for a desorbtion of a surface area of the shells. A vacuumpump can maintain a partial pressure of the vacuum in the insulationvolume to below approximately 10 millitorr. The vacuum can be providedusing a non-oil based pump. The pump can initially evacuate theinsulation volume to a total pressure of approximately 500 millitorr. Acryogenic heat exchanger can cryogenically cool the shells to atemperature below approximately −175° C. Gettered gases can be removedby a pseudo thermo/kinetic energy transfer during the rise to ambienttemperature. Each shell can be a foam material. The shells prevent heatgain energy from migrating from the outer walls to the inner walls bypresenting at least two 90 degree flow pathway changes.

Advantages of the preferred embodiment may include one or more of thefollowing. The system has a thermal insulation technique that combines ahighly non-compressible foam and traditional vacuum processingtechniques to produce a novel insulation technique. This technique canbe used to reduce the heat gain properties of a low temperature vesselsand allow for the manufacture of square, flat walled vacuum chambersthat demonstrate no structural deformation or metal fatigue during theevacuation process. The theoretical R-value of this technique is greaterthen 100 as measured by the International System of Units—RSI.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an exemplary process to insulate a vessel.

FIG. 2 shows an exemplary shell arrangement.

FIG. 3 shows an assembly of the vessel with outer walls, shells, and thepayload chamber.

FIG. 4 shows an exemplary payload chamber enclosed by the shell.

FIG. 5 shows an exemplary cold vacuum processing operation.

DESCRIPTION

FIG. 1 shows an exemplary process to insulate a vessel such as abiological storage chamber, among others. The process forms a pluralityof foam shells on all sides of a vessel without a direct energy pathwayfrom outer walls of the vessel to the inner walls of the vessel (1).Next, the process places the foam shells under vacuum (2). The processthen cryogenically cools the foam shells (3); and while under vacuum,allowing the foam shell temperature to rise from a cryogenic temperatureto an ambient temperature (4).

FIG. 2 shows an exemplary shell arrangement. The shell can be made offoam, among other materials. In FIG. 2, two outside back shell portions25 and 26 are positioned adjacent each other. Portions 25 in turn facesinner back shell portions 27 and 33. These portions in turn aresurrounded on left and right sides by a pair of side shell assemblyhaving an outside side shell portions 28 and 29 that face inside sideshell portions 30 and 31. The back shell portions and the side shellportions are in turn connected to top and bottom shell assemblies. Thebottom shell assembly includes outer bottom shelf portions 19 and 34facing inner bottom shelf portions 20-21. The top shell assemblyincludes outer top shelf portions 22 and 32 that face inner top shelfportions 23-24. The top shell assembly include openings 22 that allowcryogenic coolants to enter and exit a payload chamber as shown in moredetails below.

In one embodiment, each foam piece is four inches thick and is made froma polyisocyanurate material. The vacuum vessel is made of austeniticstainless steel, type 302, 304, 316, 321 or 347. The foam design placesfoam sections on all sides of a vessel and will be designed so thatthere are no direct energy pathways from the outer walls to the innerwall. The arrangement challenges any heat gain energy from migratingfrom the outer wall to the cryogenically tempered inner surface bypresenting at least two 90 degree flow pathway changes. All energymigrating from outer to inner is gettered by the kinetic properties ofthe foam, while in molecular flow regime. All foam sections will havevacuum pathways milled into them which are 0.065″ in cross section,spaced in an arrangement that facilitates the evacuation of the trappedspaces of the foam sections and allowing for the desorbtion of thesurface area of the foam to a minimum of 100 monolayers in oneembodiment. After the milling operation, the foam itself has enoughsurface area and flow obstructions as to prevent serious back flow ofcontaminates into the vacuum space. Vacuum channels are placed on thefoam to allow for two processes to happen. First, the channelsfacilitate the general evacuation of the chambers and second, thechannels facilitate the desorbtion of water vapor from the foam surface.The vacuum processing reduces the partial pressure of the vacuum vesselto a point lower than 10 millitorr as measured by a thermocouple orsimilar total pressure gauge. The use of non-oil based vacuum pumpsprevents the back streaming of residual water and oil vapor with itscontaminating gas load.

In addition to using oil free vacuum pumps, a cold processing techniqueis applied to the shells. The technique includes of three separatesteps.

Firstly, the assembly is evacuated to a total pressure of approximately500 millitorr. The specific ultimate pressure is not important.

Secondly, the assembly is then cryogenically cooled to a temperature ofno more then −175° C. as measured on the inner wall of the vacuumchamber. This getters contaminant gases onto the inner wall of thevacuum chamber via thermodynamic processes, thus conditioning the foam.

Lastly, while the vacuum pump system is connected and applied to thevacuum chamber, the temperature is allowed rise to ambient. The vacuumpump removes all of the gettered gases by way of a pseudo thermo/kineticenergy transfer.

The following examples are intended to explain the invention in greaterdetail, but without limiting it in its scope. In one exemplaryembodiment, the foam is a Polyisocyanurate Insulation that has thefollowing specifications:

-   -   Compressive Strength 3 D 1621 lb/in2 kPa    -   Parallel to Rise (Thickness) 140 970    -   Perpendicular to Rise (Width) 130 900    -   Perpendicular to Rise (Length) 130 900    -   Compressive Modulus D 1621 lb/in2 kPa    -   Parallel to Rise (Thickness) 3100 21400    -   Perpendicular to Rise (Width) 2800 19300    -   Perpendicular to Rise (Length) 2800 19300    -   Shear Strength C 273 lb/in2 kPa    -   Parallel to Rise 80 550    -   Shear Modulus C 273 lb/in2 kPa    -   Parallel to Rise 800 5500    -   Tensile Strength D 1623 lb/in2 kPa    -   Parallel to Rise (Thickness) 80 550    -   Tensile Modulus D 1623 lb/in2 kPa    -   Parallel to Rise (Thickness) 2800 19300    -   Flexural Strength C 203 lb/in2 kPa    -   Parallel to Rise 160 1100    -   Flexural Modulus C 203 lb/in2 kPa    -   Parallel to Rise 5800 40000    -   k-Factor (75° F. (24° C.) mean temp.) C 518    -   BTU·in/hr·ft2·° F. W/m° C.    -   Initial 0.180 0.026    -   Aged 180 days @ 75° F. (24° C.) 0.200 0.029    -   R-Value/in (75° F. (24° C.) mean temp.) C 518    -   Hr·ft2·° F./BTU m2·° C./W    -   Initial 5.5 0.97    -   Aged 180 days @ 75° F. (24° C.) 5.0 0.88    -   Closed Cell Content D 2856% 97% 97    -   Water Absorption C 272% by Volume 0.7% by Volume 0.7    -   Water Vapor Permeability E 96 Perm-Inch 1.1    -   (ng/Pa·s·m) 1.6    -   Dimensional Stability 4 D 2126    -   @ −40° F. (−40° C.), 7 days    -   Length % Change −0.3% Change −0.3    -   Volume % Change −0.1% Change −0.1    -   @ 158° F. (70° C.)/97% Relative Humidity, 7 days    -   Length % Change 0.4% Change 0.4    -   Volume % Change 0.7% Change 0.7    -   @ −10° F. (−23° C.), 7 days    -   Length % Change −0.2% Change −0.2    -   Volume % Change −0.7% Change −0.7    -   @ 300° F. (149° C.), 7 days    -   Length % Change −0.4% Change −0.4    -   Volume % Change −1% Change −1    -   Service Temperature 5° F. −297 to +300° C. −183 to +149

FIG. 3 shows an assembly of a vessel 110 with outer walls, shells, andinner walls formed by the exterior of the payload chamber. FIG. 3 showsthe five-sided outer “tub” 110A assembled with a lining of insulation,into which is inserted metal inner “tub” 124, typically of 16 gaugestainless steel, having a front flange which extends around theperimeter. This is seamlessly laser-welded to the alter tub 110 allaround in a no leak manner to form an insulation tub 110B with the fivehollow walls totally enclosed and filled with the shell portions 112,122, 116, 118, 120 and 122. More details on the vessel 110 are disclosedin co-pending application Ser. No. 11/890,451, filed on Aug. 7, 2007,the content of which is incorporated by reference.

FIG. 4 shows an exemplary assembled payload chamber enclosed by aninsulation volume where the shells are placed. In one embodiment, thisshell portions can be first purged of moisture at 120 degrees C. thenevacuated at 100 degrees C. to a vacuum of approximately 0.0002 torr(i.e. 02 millitorrs, 1 torr=1/760 atmosphere) and then sealed off as avacuum-insulation-walled enclosure.

The rigidity and high compressive strength of the shell material serveto counteract and minimize inward bending distortion of the two opposedmetal sheets due to stress from the internal vacuum and externalatmospheric pressure as the shell material provides sufficientcompressive strength.

FIG. 5 shows an exemplary cold vacuum processing operation. First, thevessel is constructed (200) and a visual inspection is done (202) inaccordance with a manufacturing protocol (204). If the visual inspectionpasses, a primary evacuation operation is done (206). The primaryevacuation can be done using a mechanical pump (208). After the primaryevacuation, a pressure reading is done (210). The reading tests that atotal pressure of about 500 millitorr is in the chamber within 60minutes (212). Next, the system performs a leak check using anatmospheric helium leak detector (222). The system confirms that theleak rate is less than 10 e-6 atm-cc/sec in one embodiment (223). Next,the system is cooled to less than −175 degree C. (224) while a continualvacuum pumping dual stage turbo molecular pump is operated (225). Next,a pressure reading is taken (226). Preferably, the pressure is less than10 millitorr (228). The system also checks for leak using theatmospheric helium leak detector (230). The helium leak rate isascertained (232). The temperature of the vessel is then allowed to riseto ambient temperature while under vacuum (234). A final ultimatepressure evacuation is done (236) and the vessel is sealed (240).

Although the invention has been described in detail in the foregoing forthe purpose of illustration, it is to be understood that such detail issolely for that purpose and that variations can be made therein by thoseskilled in the art without departing from the spirit and scope of theinvention except as it may be limited by the claims.

What is claimed is: 1) A cryogenic processor apparatus, comprising: a)an outer housing; b) an inner housing coupled to the external housing todefine a vacuum region there between; c) material disposed in the vacuumregion to provide redundant insulation and structural support at acryogenic temperature. 2) The apparatus of claim 1, wherein the materialcomprises an insulation material with one of: a silica micro balloon,polyisocyanurate. 3) The apparatus of claim 1, wherein the vacuum regionis processed using a novel method of removing residual water vapor andother partial pressure of contaminants. 4) The apparatus of claim 1,wherein the vacuum region is evacuated to a partial pressure ofapproximately 0.2 milliTorr. 5) The apparatus of claim 1, comprising acryogenic heat exchanger with one or more tubings. 6) The apparatus ofclaim 5, where in the cryogenic heat exchanger comprises one or moretubings including redundant tubings. 7) The apparatus of claim 5,wherein the cryogenic heat exchanger comprises U-shaped tubings coveringat least three walls of the payload bay. 8) The apparatus of claim 5,wherein the cryogenic heat exchanger comprises tubings covering at leastfour sides of the payload bay. 9) The apparatus of claim 5, wherein thecryogenic heat exchanger comprises a port coupled to one or more tubingsto provide input and output connections thereto. 10) The apparatus ofclaim 5, comprising a door coupled to the payload bay, wherein the doorcomprises three or more materials having different thermalcharacteristics. 11) A method to provide ultra low temperatureprocessing and/or storage, comprising: a) providing insulation andstructural support using a material disposed in a vacuum region betweenan external housing and an inner housing; and b) cryogenicallyprocessing one or more compartments contained in a payload bay. 12) Themethod of claim 11, wherein the material comprises an insulationmaterial with silica micro balloon technology. 13) The method of claim11, comprising removing water vapor, partial pressure contaminates andatmospheric gases from the vacuum region. 14) The method of claim 11,comprising evacuating the vacuum region to approximately 0.2 millitorr.15) The method of claim 11, wherein the cryogenic heat exchangercomprises one or more heat exchange tubings. 16) The method of claim 11,wherein the cryogenic heat exchanger comprises primary heat exchangetubings including redundant tubings. 17) The method of claim 16, whereinthe redundant tubings comprise one of: tubings branched from the primaryheat exchange tubings, tubings operating in parallel with the primaryheat exchange tubings, U-shaped tubings covering at least three walls ofthe inner housing. 18) The method of claim 11, comprising providing adoor adapted to seal a chamber in the payload bay, wherein the doorcomprises a plurality of materials each having different thermalcharacteristics. 19) The method of claim 11, comprising providing achangeable rack assembly in the chamber. 20) The method of claim 19,comprising transmitting energy from the payload bay into the heatexchanger through the changeable rack assembly. 21) The method of claim11, comprising providing a negative pressure in the payload bay. 22) Themethod of claim 21, comprising providing pneumatic seals on the maindoor assembly and cryogenics vacuum pumping through the heat exchangerto remove thermal energy from the payload bay and into the heatexchanger. 23) The method of claim 1, wherein at least one of theexternal housing and the inner housing comprises a flat surface.